Manchin is facing a competitive re-election contest in a deeply red state that voted more heavily for Trump than any other state in the country. His new advertisement shows that there has been a shift in the politics of ObamaCare in recent years.

The popular incumbent Democrat has put protecting ObamaCare (also known as the Affordable Care Act, or ACA) at the the very center of his campaign. The main provision of the health care law which he wants to support is the protection it offers for people with pre-existing health conditions.

There is a federal lawsuit to overturn the ACA using the claim that its requirements violate the U.S. Constitution. It is this lawsuit that Manchin “shoots down” in his new ad.

His opponent, West Virginia Attorney General Patrick Morrisey, takes the typical Republican position of supporting the the lawsuit which would have the effect of denying millions of Americans the health insurance coverage they need.

“That’s me shooting the cap and trade bill, because it was bad for West Virginia,” Manchin says in the ad, showing the opening from the 2010 spot, where Manchin rebelled against an environmental priority of Democratic leaders.

“Now the threat is Patrick Morrisey’s lawsuit to take away health care from people with pre-existing conditions,” Manchin continues. “He is just dead wrong, and that ain’t gonna happen.”

Morrisey claims that he wants people with pre-existing health conditions to have coverage, but he also has said that he strongly supports the “repeal and replace” of the ACA.

Morrisey’s claims ring hollow, however, since an ObamaCare replacement that includes similar pre-existing condition protections is a theory that will never become a reality. To make that happen, a Republican Congress would have to agree on the replacement program, which they have never been able to do. In fact, the proposed GOP replacement bills in 2017 would have allowed states to waive pre-existing condition protections for their citizens. They would be likely to do this under pressure from the health insurance lobby, because health insurance companies make greater profits when they are allowed to deny coverage to people with any sort of health condition.

Manchin was thought to be one of the most vulnerable Senate Democrats running for reelection in 2018 because Trump West Virginia won by more than 40 percentage points in the 2016 presidential election.

Democrats are finding that the rising popularity of the ACA is a potent political issue that benefits them in the 2018 midterms.

Other Senate Democrats running for re-election in pro-Trump states have also been attacking Republicans for supporting the anti-ObamaCare lawsuit.

Arguments in the case took place last week in federal court in Texas. The case is being supported by 20 states that are under Republican rule. It is being presided over by a conservative judge who in arguments last week showed skepticism of the arguments being made by the ObamaCare supporters’ attorneys. If he issues an initial ruling against the ACA it would likely be overturned on appeal, but in the meantime it may very well impact November’s elections.